An ultrasound diagnostic apparatus iteratively transmits ultrasonic waves from an ultrasound probe to a subject at the time interval, the ultrasound probe receives reflection echo signals on time series corresponding to the iterative transmission of the ultrasonic waves, a receiving-signal processing unit generates high-frequency (RF) frame data corresponding to arbitrary tomographic planes of the subject on time series on the basis of the received reflection echo signal, and tomographic images (e.g., B-mode images) on time series are restructured and displayed on the basis of the RF frame data, thereby using the ultrasound diagnostic apparatus for medical diagnosis.
For the above-mentioned ultrasound diagnostic apparatus, in recent years, such a technology is proposed that the elastic modulus and strain of the body tissue in the diagnostic part are measured and are displayed as an elasticity image (refer to e.g., Patent Document 1). As mentioned above, the subject is iteratively pressurized (compressed and decompressed), the elasticity image is obtained with the strain of the body tissue of the subject due to the pressure on the basis of two pieces of the FR frame data on time series, the elasticity (strain or elastic modulus) of each part of the body tissue is obtained, and the elasticity image is displayed in a display format (color image or binary image) corresponding to the level of elasticity.
In the medical diagnosis, in the case of diagnosing the diseased tissue such as cancer, a specific substance in the blood having a relationship with the diseased tissue is generally examined with blood drawing. For example, as diagnosis of the prostate cancer, PSA (Prostate Specific Antigen) examination is well-known. The PSA is a substance generated in the prostate, so-called prostate-specific antigen. In the case of the prostate cancer, the blood level increases and the blood of a patient is therefore sampled and the blood level in the PSA is examined, thereby diagnosing the prostate cancer. The PSA examination can be performed only with the blood sampling. Thus, in the case of suspecting the prostate cancer, the PSA examination is first performed and a patient having a high PSA value undergoes the ultrasonography or MRI examination.
However, even if the PSA value is high, a cancer cannot determined by the examination using the ultrasound image or MR image. Therefore, the organ of prostate is directly sampled with an invasion device such as a paracentesis needle, thereby performing the diagnosis (cytology). However, upon sampling the organ of the lesion, the lesion which is suspected to have a cancer cannot be specified out of the body. As a consequence, the paracentesis is actually executed to the lesion at random plural times. The number of paracentesis times is varied depending on the medical facility. Further, even with the paracentesis, a cancer cell cannot be found. Therefore, there is a problem that the examination takes a long time and the operation strains the patient.
Herein, the lesion of the cancer, etc. has the elasticity of organ higher than that of the normal organ around the lesion. Therefore, an elasticity image indicating the hardness of organ with an ultrasound diagnostic apparatus is formed, thereby enabling the position of the lesion to be specified. Then, upon invading a paracentesis needle in the living body, a color elasticity image of the lesion is superposed to a B-mode tomographic image and the resultant image is displayed as a reference image. Then, it is expected that this operation supports the paracentesis operation of the paracentesis needle into the lesion.    Patent Document 1: JP No. 2000-60853 A